<html>
	<head>
		<title></title>
	</head>
	<style>
		body{
			border: 1px solid #333;
		}
		.box{
			width: 200px;
			height: 200px;
			background: red;
			
			margin: 0 auto;		/*水平居中对齐*/
		}
	</style>
	<body>
		<div class="box"></div>
	</body>
</html>